The instant invention solves the vexatious thermal management problems that have, to date, plagued hydrogen storage bed systems. The revolutionary design includes an integrated thermal management system which evenly and efficiently heats and cools hydrogen storage alloys that are able, for the first time to realistically use the most ubiquitous, ultimate source of fuel for the next millennium and beyond, hydrogen. More particularly, there is described the integration of heat generators, such as catalytic combustors, cooling devices, such as heat exchangers, and a heat distribution system, such as thermal bus bars or heat pipes in combination with heat distribution fins.
Hydrogen, as a fuel, has enormous energy capacity and, when oxidized or burned, produces only water as a product of that combustion. The facts of its ease of burning, its effectively pollution-free burning, combined with the relative ease of modification of existing power sources, including the internal combustion engine makes hydrogen an ideal source of energy for energy-hungry economies. Stanford Ovshinsky and his research teams with Energy Conversion Devices have long recognized the potential value of hydrogen as the ultimate fuel. In light of that recognition, development efforts have continued in support of means for storage (U.S. Ser. No. 09/435,497 filed Nov. 6, 1999) and transportation of hydrogen including an infrastructure in support of a hydrogen economy (U.S. Ser. No. 09/444,810 filed Nov. 22, 1999).
While hydrogen is the ultimate fuel, its storage and transportation presents difficulties. In the liquid state, hydrogen is subject to severe losses due to vaporization; additionally there is an initial high energy cost in compression and refrigeration to attain its liquid state. In the gaseous state, to approach economic storage capacities, hydrogen must be compressed, containment of such compressed gas requires heavy-walled containers which themselves must be heavy and of sturdy build. The Ovshinsky teams have addressed these needs, as noted above, through development of hydrogen storage alloys; metals and metallic alloys having high storage capacity for hydrogen as well as high rates of hydrogen charging and discharging at comparatively low temperatures.
The development of such high-capacity solid storage material in which the hydrogen is stored within the molecular or crystalline structure of the material has been key to solution of a related yet still different concern within a hydrogen-energy based economy. That is the dependable, repeatable storage and release of hydrogen in small quantities for portable uses, especially for portable motive power needs. For such applications, it is necessary to be able to reliably and efficiently fully charge the storage material and discharge the same which is on-board to run the motive power source which may be a hydrogen combustion engine, hydrogen fuel-cell running an electric motor, or other hydrogen-consuming motive system. Coupled with these needs is a need to assure that such a system and its container is able to withstand the constant vibration associated with motive transportation. As previously described by the Ovshinsky teams, metal hydride materials have recently become a focus of general interest as a means of solid-state hydrogen storage generally and for reliable on-demand or as-needed storage and dispensing of hydrogen for motive power in transportation applications.
Energy production for motive power is a large and growing fraction of the contribution of troublesome xe2x80x9cgreenhouse gasesxe2x80x9d being constantly added in huge volumes to the Earth""s atmosphere. Of these, carbon dioxide, being produced in greater volumes, is particularly onerous of these simply because it is produced in extremely large volumes as a product of combustion of carbon-based fuels, as well as carbon monoxide, another of the greenhouse gases carrying additional burdens of toxicity during respiration. Use of hydrogen as a fuel simply eliminates the production of the oxides of carbon and produces only water as a product of its combustion. Replacement of gasoline, liquefied petroleum gases (LPG""s), alcohols, fuel oils, or other carbon-based fuels with hydrogen, particularly in motive fuel applications, will provide tremendous reduction in the production and release of such global-warming and toxic materials.
As noted in the previously mentioned ""810 application, careful thermal management of the hydrogen storage material is critical to the reliable cycling of hydriding and dehydriding, or charging and discharging of metal hydrides or other storage materials. The inventors now provide here means for controlling the release of heat during charging or refueling as well as generating and controlling the application of heat during discharge or use of the fuel from the on-board storage container or bed of hydrogen storage material. These inventors have developed and now disclose means for selectively or evenly heating or cooling the storage bed as needed for both use in transit for power generation and refueling of the xe2x80x9cgas tankxe2x80x9d at the xe2x80x9cfilling stationxe2x80x9d. This is accomplished by design of heating and cooling means, or combinations thereof with in the bed of storage material coupled with means for conveying heat or cooling capacity to distant areas in such a storage bed. Also of consideration, and part of the below-described invention is thermal insulation of the inside of the storage container from the atmosphere to assure that the thermal management is conducted as intended for smooth operation of whatever motive vehicle is being operated from such a fuel-storage bed.
Additionally, the storage containers of this invention may be sized in generally infinite volumes and dimensions, they may also be combined into systems by addition of multiple usefully-sized containers. Effectively, the inventors here have developed and now provide hydrogen fuel carrying and storage capacity for motive vehicles of any use, shape, or size including, but not limited to cars, trucks, trains, aircraft and watercraft. Application of hydrogen fuel to move these vehicles will be a large step toward serious and useful reduction of the currently, and sometimes catastrophically, occurring global warming.
The instant invention comprises a hydrogen storage bed system which includes a pressure container, a hydrogen storage alloy disposed within the pressure container, and an integrated thermal management system integrally disposed within the pressure container. The integrated thermal management system includes heat generation means, cooling means, and heat distribution means.
The heat generation means one or more of electrical heating elements and catalytic combustors, with the latter preferred. The catalytic combustors are designed to combust one or more of hydrogen, gasoline, fuel oil, propane, diesel fuel, or natural gas, with propane and hydrogen preferred. The cooling means comprises a tube-type heat exchanger designed to utilize air, hydrogen, water or organic coolants. Air, hydrogen and water are the preferred coolants. The heat generation means and the cooling means can be combined into a single unit designed heat and cool.
The heat distribution means can include heat sinks thermally coupled to both said heat generation means and said cooling means and heat distribution fins thermally coupled to said heat sinks and dispersed within the hydrogen storage alloy. The heat distribution fins and heat sinks are formed from a material selected from the group consisting of thermally conductive graphite, stainless steel, magnesium and magnesium alloys. Alternatively, the heat distribution means can include heat pipes thermally coupled to both said heat generation means and said cooling means instead of heat sinks. The heat distribution fins thermally coupled to the heat pipes and dispersed within the hydrogen storage alloy. Once again, the heat distribution fins are formed from a material selected from the group consisting of thermally conductive graphite, stainless steel, magnesium and magnesium alloys.
The hydrogen storage alloy is selected from the group consisting of T-Zr based alloys and Mg based alloys. The preferred high capacity Mg-based storage alloys contain greater than about 90 weight % magnesium, and contain at least one modifier element. The at least one modifier element creates a magnesium based alloy which is capable of storing at least 7 weight % hydrogen and is capable of absorbing 80% of the full storage capacity of hydrogen in under 1.5 minutes at 300xc2x0 C. The modifier elements mainly include Ni and Mm (misch metal) and can also include additional elements such as Al, Y and Si. Thus the alloys will typically contain 0.5-2.5 weight % nickel and about 1.0-4.0 weight % Mm (predominantly contains Ce and La and Pr). The alloy may also contain one or more of 3-7 weight % Al, 0.1-1.5 weight % Y and 0.3-1.5 weight % silicon. The hydrogen storage alloy is in the form of powder, pellets or a mixture thereof, with the latter preferred.
The pressure container is formed from one or more materials selected from the group consisting of stainless steel or fiber reinforced polymers. The preferred pressure container is a multilayer structure, such as a three layered structure which includes 1) an inner layer formed form a lightweight material which is non-reactive with hydrogen and said storage alloy, and can withstand the operating temperature of the system, 2) a middle layer formed from a lightweight insulating material; and 3) an outer layer formed from a fiber reinforced polymer composite material which contains the operating pressure of the bed system.
The hydrogen storage bed system may also include thermocouples disposed throughout the interior of the hydrogen storage alloy to determine the state of charge of the system by observing temperature spikes in discharged areas of the alloy.
Finally, the system may include a hydrogen gas distribution system to enhance the speed of hydriding/dehydriding of the storage alloy. The distribution system typically includes a distribution manifold and one or more hydrogen permeable gas distribution tubes.